ABSTRACT The Transgenic and Knockout Mouse Shared Resource provides DCI members comprehensive and user- friendly services for the production of custom designed, genetically altered, transgenic and gene targeted mice, as well as the ability to cryopreserve these valuable reagents for storage & distribution to the scientific community. The Resource is organized into three teams of specialized personnel who provide the following services: 1) BAC recombineering service, 2) transgenic and gene targeted mouse service, and 3) rodent husbandry service. Each team of experts functions as working partners with basic and clinician scientists at the bench. These teams can also provide personalized technical support at all stages of the production process, including new approaches to conditional mutagenesis, breeding, and the use of related mutant mice or cells that are already available from other resources located worldwide. The Shared Resource offers the following services: construction & design of embryonic stem cell (ESC) targeting vectors by BAC Recombineering, with primers for screening & control vector; ESC targeting, selection, PCR Screening with expanding & freezing multiple clones; validation of targeted clones by SA & LA PCR & Southern blotting; injection of validated ESC clones to create chimeric mice; breeding & expansion of chimeric mouse lines; cryopreservation of mouse embryos & sperm; and DNA microinjection to produce transgenic mice; and related activities. Use of the Resource is tracked by service. While the Resource's cryopreservation, breeding, and rederivation service has a broad pool of users, the vast majority of users of the BAC recombineering and ES targeting services are DCI members. Attesting to the scientific impact of the Resource, 139 peer-reviewed research papers from DCI members were published during the funding period using mice generated by this Shared Resource and/or cells derived from them. The Resource is currently using institutional support to explore new CRISPR/cas methods of creating genetically altered animals. The Transgenic and Knockout Mouse Shared Resource has the following objectives: (1) to continue to provide high quality services in support of investigators' needs, and (2) to continue to explore and implement cutting edge technologies and cost effective services to meet DCI members' needs.